Happy Sunday, everyone! And, thank you for 1000 followers :) I promised Iâd write up a new post for those of you who just started following me, so enjoy this video of one of my black sex-link hens, the Queen, being cute and dust-bathing in the sun.
I think everyone here on birdblr loves to watch their birbs bathe, whether itâs done in water or a nice patch of dirt. Some bird species have no problem bathing in either, but most, if not all gallinaceous birds (poultry, including chickens and quails) will only dustbathe. Why do they do it - how does rolling around in dirt keep you clean?
The most common answer people will give you is that dustbathing keeps ectoparasites - mites and lice - off a chickenâs skin and feathers. While this has been common knowledge among both chicken farmers and backyard chicken owners for decades, you might be surprised to learn that no one ever actually tested this scientifically until 2012. There are possibly hundreds of studies which basically tell us that dry dirt or sand is just like dry shampoo for the birds, absorbing excess oil from their feathers, and removing it once the dust is shaken, or ârousedâ out. Certain species of avian mites and lice feed primarily on the oil, so it was believed that regularly removing it would leave the parasites without a food source, if the physical movements involved in dustbathing behaviour didnât dislodge them first. Martin and Mullens were the first researchers to actually test and support the hypothesis that dustbathing behaviour evolved, at least in part, specifically for the purpose of reducing the number of parasites on a birdâs body. Their work also showed that sulfur, which is among one of the many naturally occurring elements in dirt, plays a big role in keeping parasites away by killing them through direct contact and possibly fumigation. So, there is solid evidence that dustbathing helps with parasite control, although no one ever really bothered looking into it, for some reason.
What was more commonly studied was the effect of dustbathing on a chickenâs feathers. By removing all of that excess oil, down feathers in particular become fluffier as a result (side note: this is also one of the few instances where the word âfluffyâ is used in a scientific paper). This increases the overall insulation ability of the plumage, and hens housed on an appropriate dustbathing substrate have been shown to have lower temperatures on their backs (important for keeping cool on hot days like today!).
Hereâs the not-so-cute, kinda depressing part of this post. We know that dustbathing has all these hygiene-related benefits for the birds. So why are hens kept on commercial egg farms (note: Iâm only speaking based on current Canadian poultry industry practices) not given anything to dustbathe on? Generally, commercial birds who never get the chance to go outside donât become exposed to ectoparasites, which most farmers are only concerned about because they can cause a hen to lay fewer eggs per year. Barring that, itâs argued that there just isnât any other reason to give hens a chance to dustbathe. Thatâs where animal welfare researchers come in (and thatâs why I love my job). In the last few decades, there have been a plethora of studies showing that hens kept in wire cages will âshamâ dustbathe, or perform dustbathing behaviours when there is no dust to begin with. At that point, the behaviour becomes labelled as âabnormalâ, indicating that the animal has some need that is not being met. Other studies have demonstrated numerically how much work a hen will put in to dustbathe - for example, some experiments involve hens learning to push through heavy doors (up to a certain percent of their own body weight) just to access a pan of peat to dustbathe in. Finally, a fascinating study done very recently showed that dustbathing quail had a higher tendency of exhibiting possible facial indicators of positive emotions (i.e. dustbathing birb = birb with poofier face = possibly happy birb). With such a large body of solid, scientific evidence to support a significant emotional significance of expressing proper dustbathing behaviour in birds (I donât know about you, but there are days when a nice bath/shower is more about stress relief and self-care than just keeping clean), researchers have been able to effectively argue for providing dustbathing opportunities to commercial laying hens. In Canada, battery cages will be banned from all egg farms by 2036, and replaced by âenriched housingâ, which will be required to include, among other things, a small area for dustbathing behaviour.
So, while it may sound annoying at times when researchers like me say things like âthere is/isnât any scientific evidence for xâ, the reason we need to look for that solid evidence is that itâs the only thing that industries and the public will listen to, and often itâs the only thing that can bring about positive (but small) change!
Bertin A, Cornilleau F, Lemarchand J, Boissy A, Leterrier C, Nowak R, Calandreau L, Blache MC, Boivin X, Arnould C, Lansade L. Are there facial indicators of positive emotions in birds? A first exploration in Japanese quail. Behavioural processes. 2018 Jun 30.
Martin CD, Mullens BA. Housing and dustbathing effects on northern fowl mites (Ornithonyssus sylviarum) and chicken body lice (Menacanthus stramineus) on hens. Medical and veterinary entomology. 2012 Sep;26(3):323-33.
Van Liere DW, Bokma S. Short-term feather maintenance as a function of dust-bathing in laying hens. Applied Animal Behaviour Science. 1987 Aug 1;18(2):197-204.
Wichman A, Keeling LJ. Hens are motivated to dustbathe in peat irrespective of being reared with or without a suitable dustbathing substrate. Animal behaviour. 2008 Apr 1;75(4):1525-33.
https://www.eggfarmers.ca/press/egg-farmers-of-canada-announces-industry-wide-transition-away-from-conventional-housing/
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